ACPAtmospheric Chemistry and PhysicsACPAtmos. Chem. Phys.1680-7324Copernicus GmbHGöttingen, Germany10.5194/acp-13-11757-2013Quantification of waves in lidar observations of noctilucent clouds at scales from seconds to minutesKaiflerN.1BaumgartenG.1FiedlerJ.1LübkenF.-J.11Leibniz Institute of Atmospheric Physics at the Rostock University, Kühlungsborn, Germany0412201313231175711768This work is licensed under a Creative Commons Attribution 3.0 Unported License. To view a copy of this license, visit http://creativecommons.org/licenses/by/3.0/This article is available from http://www.atmos-chem-phys.net/13/11757/2013/acp-13-11757-2013.htmlThe full text article is available as a PDF file from http://www.atmos-chem-phys.net/13/11757/2013/acp-13-11757-2013.pdf

We present small-scale structures and waves observed in noctilucent
clouds (NLC) by lidar at an unprecedented temporal resolution of
30 s or less. The measurements were taken with the
Rayleigh/Mie/Raman lidar at the ALOMAR observatory in northern
Norway (69° N) in the years 2008–2011. We find multiple layer
NLC in 7.9% of the time for a brightness threshold of
δ β = 12 × 10<sup>&minus;10</sup> m<sup>−1</sup> sr<sup>−1</sup>. In comparison
to 10 min averaged data, the 30 s dataset shows
considerably more structure. For limited periods, quasi-monochromatic
waves in NLC altitude variations are common, in accord with
ground-based NLC imagery. For the combined dataset, on the other hand,
we do not find preferred periods but rather significant periods at all
timescales observed (1 min to 1 h). Typical wave
amplitudes in the layer vertical displacements are 0.2 km with
maximum amplitudes up to 2.3 km. Average spectral slopes of
temporal altitude and brightness variations are −2.01 ± 0.25 for
centroid altitude, −1.41 ± 0.24 for peak brightness and
−1.73 ± 0.25 for integrated brightness. Evaluating a new single-pulse
detection system, we observe altitude variations of 70 s
period and spectral slopes down to a scale of 10 s. We
evaluate the suitability of NLC parameters as tracers for gravity
waves.